Psoriasis, a chronic inflammatory skin disease affecting 3-4% of the global population, is characterized by red patches with white scales. Its etiology is complex, involving genetic and environmental factors. Oxidative stress, an imbalance between reactive oxygen species (ROS) production and antioxidant capacity, is a significant risk factor. Elevated ROS damages cellular components and activates inflammatory pathways, contributing to psoriatic inflammation. Psoriasis patients exhibit increased ROS production and decreased antioxidant capacity, correlating with disease severity. The inflammatory response and keratinocyte hyperplasia are exacerbated by ROS and free radicals. Therefore, exogenous antioxidant supplementation is a potential therapeutic strategy. Sulforaphane (SFN), a natural isothiocyanate found in cruciferous vegetables, possesses potent antioxidant and anti-inflammatory properties. Studies have demonstrated its ability to inhibit cell proliferation, induce apoptosis, and modulate gene expression by targeting various signaling pathways, including HDAC, DNMT, and NF-κB. SFN's effects on NRF2 and microRNAs have also been documented. However, its role and mechanism of action in psoriasis remain unclear. This study aims to investigate SFN's modulatory effects in an imiquimod (IMQ)-induced psoriatic mouse model and elucidate the underlying molecular mechanisms, focusing on the potential involvement of the KEAP1-NRF2 pathway and its impact on oxidative stress in psoriatic lesional skin. We hypothesize that SFN protects against cutaneous inflammation in an NRF2-dependent manner.

Existing literature extensively documents the role of oxidative stress in psoriasis pathogenesis. Studies have shown increased ROS production and decreased antioxidant capacity in psoriasis patients, linking oxidative stress to disease severity and duration. The contribution of ROS to keratinocyte hyperplasia and inflammation is well-established. Sulforaphane (SFN) has demonstrated antioxidant and anti-inflammatory properties in various contexts, including cancer and other chronic inflammatory diseases. Its mechanisms of action involve modulation of various signaling pathways, including NF-κB, and regulation of NRF2 and microRNAs. However, the specific role of SFN and its underlying mechanism in psoriasis were previously undefined, creating a gap in knowledge that this study aims to address.

The study employed a multi-faceted approach involving both in vivo and in vitro experiments. **Clinical Samples:** Skin biopsies were collected from five psoriasis patients and five healthy controls. Ethical approval was obtained, and informed consent was secured from all participants. **IMQ-Induced Psoriatic Mouse Model:** Six-week-old female BALB/c, C57BL/6, and NRF2 knockout mice were used. Mice were treated with topical 5% imiquimod (IMQ) cream daily for seven days to induce psoriasis-like symptoms. The control group received vaseline cream. The SFN treatment group received daily intraperitoneal injections of SFN (5 mg/kg). Psoriasis Area and Severity Index (PASI) scoring was used to assess disease severity. Spleen index (spleen weight/body weight) was also measured. **Western Blot Analysis:** Protein expression levels of various markers (keratin 16, keratin 17, NRF2, phosphorylated NRF2, IL-1β, NQO1, phosphorylated STAT3, STAT3, phosphorylated NF-κB p65, NF-κB p65, phosphorylated IκBα, IκBα, and GAPDH) were quantified using Western blot analysis. **Histopathological Examination and Immunofluorescence Staining:** Dorsal skin samples were processed for H&E staining and immunohistochemical analysis using antibodies against keratin 16, Ki67, keratin 17, and NQO1. **Real-Time Quantitative Reverse Transcription PCR (qRT-PCR):** mRNA expression levels of IL-1β, IL-6, CCL2, IL-17a, IL-23a, and NFE2L2 were analyzed using qRT-PCR. **Cell Culture and Treatment:** HaCaT cells were treated with IL-22 and/or TNF-α to establish a psoriasis-like model. SFN was used in combination with IL-22 and TNF-α treatments to assess its effects. **Lentiviral-Based Transfection:** HaCaT cells were transfected with lentiviruses expressing shRNAs against NRF2 to generate stable NRF2 knockdown cell lines. **Measurements of Intracellular ROS:** Intracellular ROS levels were measured using dihydroethidium (DHE) staining and confocal microscopy. **Network Pharmacology:** Network pharmacology analysis was performed to predict the target molecules of SFN and identify the relevant pathways involved in its therapeutic effects. Databases used include SuperPred, OMIM, GeneCards, and STRING. **Statistical Analyses:** Statistical analyses were performed using GraphPad Prism software (version 9.0.0). One-way ANOVA or unpaired Student's t-tests were used as appropriate.

The study revealed that SFN significantly ameliorated psoriatic symptoms in the IMQ-induced mouse model. Macroscopic observations and PASI scores showed reduced erythema, scaling, and infiltration in the SFN-treated group compared to the IMQ-only group. Histopathological analysis demonstrated reduced epidermal thickness, hyperkeratosis, and dermal infiltration in SFN-treated mice. Immunohistochemical staining showed significantly lower expression of keratin 16 (K16), keratin 17 (K17), and Ki67 in SFN-treated mice, indicating reduced keratinocyte hyperproliferation and inflammation. Western blot analysis revealed that SFN treatment significantly decreased the protein levels of K16 and K17. Furthermore, SFN significantly reduced the activation of STAT3 and NF-κB pathways, as evidenced by decreased phosphorylation levels of STAT3 and IκBα. qRT-PCR analysis showed a significant reduction in the mRNA expression levels of pro-inflammatory cytokines IL-1β, IL-6, and CCL2 in SFN-treated mice. In vitro studies using HaCaT cells showed that SFN inhibited IL-22 and TNF-α-induced activation of inflammatory pathways and keratinocyte proliferation, evidenced by a reduction in p-STAT3, p-IκBα, K16, and K17. Network pharmacology analysis identified the KEAP1-NRF2 pathway as a potential mechanism for SFN's therapeutic effects. The study found decreased NRF2 expression in human psoriatic lesions, both at the mRNA and protein levels. In vivo, SFN treatment increased NRF2 and p-NRF2 expression. In vitro, SFN pretreatment restored NRF2 and p-NRF2 expression in IL-22- and TNF-α-treated HaCaT cells and decreased IL-22-induced superoxide production. Importantly, NRF2-deficient mice exhibited exacerbated psoriasis-like symptoms and reduced responsiveness to SFN treatment, confirming the critical role of NRF2 in SFN's therapeutic mechanism. Analysis of IL-17a and IL-23a expression in NRF2 deficient mice further reinforced the NRF2-dependent mechanism of SFN action.

This study provides compelling evidence supporting the therapeutic potential of SFN in treating psoriasis. The observed improvement in psoriatic symptoms, reduction in inflammatory markers, and activation of the KEAP1-NRF2 pathway strongly suggest that SFN exerts its therapeutic effects through a mechanism involving antioxidant defense and inflammation modulation. The key finding of exacerbated psoriasis in NRF2-deficient mice and the lack of therapeutic effect of SFN in these mice underscores the crucial role of NRF2 in SFN's action. The findings align with existing knowledge of the importance of oxidative stress in psoriasis and the protective role of NRF2 in maintaining skin homeostasis. The results suggest that SFN's antioxidant properties combat the oxidative stress associated with psoriasis, while its modulation of inflammatory signaling pathways (STAT3 and NF-κB) directly addresses the inflammatory component of the disease. The reduction in K16 and K17 expression further supports SFN's efficacy in normalizing keratinocyte proliferation and differentiation. The study's findings are significant as they identify a novel therapeutic strategy for psoriasis, utilizing a naturally derived compound with a promising safety profile.

This study demonstrates that sulforaphane (SFN) alleviates psoriasis-like symptoms in a mouse model primarily through the activation of the KEAP1-NRF2 pathway. This activation leads to enhanced antioxidant defense and attenuation of inflammatory signaling, resulting in reduced keratinocyte hyperproliferation and inflammation. The findings highlight the potential of SFN as a therapeutic agent for psoriasis. Future studies should investigate the long-term effects of SFN in chronic psoriasis models and conduct clinical trials to evaluate its efficacy and safety in human patients. Further research should also focus on optimizing SFN delivery methods to enhance its therapeutic impact.

The study primarily utilized a mouse model of psoriasis, which may not fully recapitulate the complexities of human psoriasis. The study focused on the acute phase of psoriasis; the long-term effects of SFN on chronic psoriasis require further investigation. The sample size for human biopsies was relatively small. Future studies with larger sample sizes and longer treatment durations are needed to confirm these findings and explore the long-term effects of SFN treatment.